fix the toyFF and add tests

pyproject.toml

@@ -53,6 +53,7 @@ pytest = "^7.1.3"
 pytest-cov = "4.0.0"
 pylint = "^3.1.0"
 pyfakefs = "^5.2.3"
+scipy = "^1.11.1"
 
 [tool.poetry.group.dev.dependencies]
 pdbpp = "^0.10.3"

src/banana/toy.py

@@ -163,22 +163,22 @@ class toyFF_unpolarized(MockPDF):
     """ToyFF from 1501.00494, Eqn. 3.3 and 3.4"""
 
     def __init__(self):
-        N_v = 0.401
-        N_s = 0.094
-        N_g = 0.238
+        N_v = 1.00881
+        N_s = 17.6255
+        N_g = 438.189
 
-        D_u = lambda x: N_v * x ** (-0.963) * (1 - x) ** 1.370
-        D_ub = lambda x: N_s * x**0.718 * (1 - x) ** 6.266
-        D_g = lambda x: N_g * x**1.943 * (1 - x) ** 8
+        xD_u = lambda x: x * N_v * x ** (-0.963) * (1 - x) ** 1.370
+        xD_ub = lambda x: x * N_s * x**0.718 * (1 - x) ** 6.266
+        xD_g = lambda x: x * N_g * x**1.943 * (1 - x) ** 8
 
         self.xpdf = {}
-        self.xpdf[-3] = D_ub
-        self.xpdf[-2] = D_ub
-        self.xpdf[-1] = D_u
-        self.xpdf[0] = D_g
-        self.xpdf[1] = D_ub
-        self.xpdf[2] = D_u
-        self.xpdf[3] = D_ub
+        self.xpdf[-3] = xD_ub
+        self.xpdf[-2] = xD_ub
+        self.xpdf[-1] = xD_u
+        self.xpdf[0] = xD_g
+        self.xpdf[1] = xD_ub
+        self.xpdf[2] = xD_u
+        self.xpdf[3] = xD_ub
         self.xpdf[21] = self.xpdf[0]
         self.name = "ToyFF_unpolarized"
 

tests/test_toy.py

@@ -1,3 +1,6 @@
+import numpy as np
+from scipy.integrate import quad
+
 from banana import toy
 
 pdf = toy.mkPDF("", 0)
@@ -24,3 +27,16 @@ def test_xf():
             for x in [0.1, 0.2]:
                 assert pdf.xfxQ2(pid, x, Q2) == pdf.xfxQ(pid, x, Q2)
             assert pdf.xfxQ2(pid, 2, Q2) == 0
+
+
+def test_toyFF():
+    """Test the ToyFF_unpolarized with Eqn. 3.4 from 1501.00494."""
+    ff = toy.mkPDF("ToyFF_unpolarized", 0)
+
+    val_u = quad(lambda x: ff.xfxQ2(2, x, 1), 0, 1)[0]
+    val_d = quad(lambda x: ff.xfxQ2(1, x, 1), 0, 1)[0]
+    val_g = quad(lambda x: ff.xfxQ2(21, x, 1), 0, 1)[0]
+
+    np.testing.assert_allclose(val_u, 0.401, atol=1e-4)
+    np.testing.assert_allclose(val_d, 0.094, atol=1e-4)
+    np.testing.assert_allclose(val_g, 0.238, atol=1e-4)